Improve storage size code, mount, unmount

Add flag parsing from recovery.fstab
diff --git a/roots.cpp b/roots.cpp
index 3bd6801..e747473 100644
--- a/roots.cpp
+++ b/roots.cpp
@@ -40,7 +40,8 @@
     while ((option = strtok(options, ","))) {
         options = NULL;
 
-        if (strncmp(option, "length=", 7) == 0) {
+        if (strncmp(option, "flags=", 6) == 0)   continue;
+		if (strncmp(option, "length=", 7) == 0) {
             volume->length = strtoll(option+7, NULL, 10);
         } else {
             LOGE("bad option \"%s\"\n", option);